Topic 2 population genetics Flashcards
Phenotypes are determined by a combination of:
Genetics (heritable)
Environment
Alleles defined
- Individuals have 2 sets of chromosomes
- Each chromosome has a sequence of genes along its length.
- Alleles -
Define Homozygous
the same allele on both chromosomes.
Define heterozygous:
: different alleles on both chromosomes.
What is gene pool
It all the alleles present in the population
What aspects of heterozygosity
Depend
- number of alleles available
- size of the population
- mating practices (clonal or sexual)
- migration patterns
What is Hardy-Weinberg equilibrium consist of
- Random mating
- No mutations
- No natural selection
- No gene flow
- A large breeding population
Genetic drift
• The fluctuation of allele frequencies due to chance alone
• Occurs in all populations, but has a stronger effect in small populations
• Extreme form - Can lead to the loss of
alleles, or fixation
What causes genetic drift
- Small populations
- Random disturbances - big storm, volcano
- Founder effects
- Bottlenecks
Founder effect
Individuals that disperse to a new area to found a new population have a subset of the alleles from the entire population, leading to a large change in allele frequencies. (i.e insects on branch)
Bottleneck effect
A rapid decrease in population size due to a disturbance or natural disaster removes some genotypes from the population, altering allele frequencies.
What are outcomes of non
Random mating
Positive assortative mating – Mate choice is based on similarity of phenotype
- Negative assortative mating – Mate choice is based on dissimilarity of phenotype
- Inbreeding – Mating with relatives at a rate greater than expected by chance
Negative assertive mating
• Avoid mating with individuals that are like yourself, either phenotypically or genetically.
• Common in Plants (Self-incompatibility)
– Stop pollen germination, or pollen tube growth
• Animals (i.e. Drosophila -fruit flies)
– Rare male advantage - females prefer males with the rarest phenotype.
– Pheromonally test each other
what is a disease caused due to interbreeding
- hemophilia
Managing endangered species –low
heterozygosity = low population
robustness
what organisms mate via selfing
Plants - selfing can occur in plants that self-pollinate (Gregor Mendel’s peas) Animals - in snails and other animals that can selffertilise
what is gene flow
The transmission of traits or
genes between populations
what is the impact of geneflow
Gene flow tends to reduce differences between populations • Rates of gene flow vary widely: compare birds to ants, sharks to moss • Good- increases genetic variability • Bad -Can swamp local selection pressure, making populations less adapted (i.e. mountain and valley eucalypts)
difference between genetic drift and gene flow
Genetic Drift and Gene flow are opposing forces: drift creates differences between populations and gene flow reduces differences between populations
what is the advantage of genetic drift
Genetic drift can by chance increase the frequency of an advantageous allele to the point where natural selection can be more effective
define Clade
A group of organisms
that have a common
ancestor i.e all mammals
have hair
what is Monophyletic clade
a
clade that includes a
common ancestor and all its
descendants.
